When the Asters Open, the Last Diner of the Year Is Serving

The goldenrod has been getting all the attention this month, and it earned it. But kneel down and look underneath it this week and you will see the purple starting. The asters are opening, and when the asters open, the last diner of the year is turning its sign around.

It helps to see the yard the way the insects see it. From March to July the garden is a strip of restaurants with something open on every block. Crocus gives way to fruit bloom, fruit bloom to clover, clover to bee balm and coneflower, each closing as the next opens. By late August the strip has mostly gone dark. The flowers that remain are largely finished flowers, pollinated, spent, quietly turning their energy to seed.

What is left flying, though, has not finished. Migrating monarchs are drifting south a garden at a time. Bumblebee colonies are raising the new queens that will carry the whole line through winter. Small native bees are still provisioning the last cells of their nests. Every one of them is running on nectar, and from here to frost, nectar means asters and goldenrod almost exclusively.

Why asters bloom so late

The asters are not late by accident. They are late on purpose, and the strategy is old and shrewd. A flower blooming in June competes with half the county for pollinator attention. A flower blooming in September has the strip to itself. The aster spends the whole summer building roots and branching stems, biding, and then opens hundreds of flower heads into a market with no competition and every remaining customer highly motivated.

Each of those flower heads is itself a crowd. Like all the daisy kin, an aster head is a composite: the purple rays around the rim are individual flowers, and the golden button at the center is packed with dozens more, each one a tiny nectar well. A single healthy New England aster can carry several hundred heads. One plant is not a dish on the menu. It is a whole page.

That density is why you will find asters working even on cool days when nothing else seems alive. The insects have done the math. Flight is expensive, and a plant that offers hundreds of fueling stops in one landing beats a scattered handful of leftover blooms every time.

The six week clock

The season's last diner keeps hours, and the hours are set by frost. From the first purple in late August to the first hard freeze is about six weeks in most of the country, a little more in mild years, less where autumn comes down early. When frost closes the kitchen, it closes for good. Nothing reopens until crocus.

For the monarchs, that clock is a flight schedule. The generation moving through your yard now is the long-haul generation, the one that flies to Mexico. It travels diner to diner, feeding as it goes, converting your asters into the fat that has to carry it over two thousand miles. A cold morning monarch parked on an aster head with its wings closed is not resting for pleasure. It is refueling on the only fuel left.

For the bumblebees, the clock is a succession plan. The old queen, the workers, and the males all die with the frost. Only the new queens survive, and only if they finish fattening in time to dig in for winter. The bumblebees you see on asters in September are disproportionately those queens, eating for the entire future of their line.

What to do about the scruffy corner

Here is where the almanac asks a small favor. Asters volunteer. They show up along fences, at bed edges, in the untidy corner behind the shed, and because they spend all summer as a nondescript green clump, they are forever being pulled or mowed in July by tidy-minded gardeners who never learn what they had. If a mystery clump has survived to show purple this week, let it stand.

Let it stand through October, in fact, scruffy as it gets. A blooming aster in late September is worth more to the yard's insect life than anything you could plant in its place, and the seed heads that follow will feed the goldfinches into November. Scruffy is the correct look for the last restaurant open.

If you want to set the table on purpose, the named varieties of New England aster and aromatic aster are easy, hardy, and shrug at drought once established. Plant them in spring, cut them back by half in early June to keep them from flopping, and then do nothing. They know their date. They have been keeping it far longer than we have been keeping calendars.

So walk the fence line this week and look for the purple under the gold. The last diner of the year is open. The regulars are already at the counter.